Move out auth config from Credential type

Author: mbg

src/start-proxy/types.ts

@@ -5,18 +5,38 @@
  */
 export type RawCredential = Partial<Credential>;
 
-/**
- * A package registry configuration includes identifying information as well as
- * authentication credentials.
- */
-export type Credential = {
+/** Usernames may be present for both authentication with tokens or passwords. */
+export type Username = {
   /** The username needed to authenticate to the package registry, if any. */
   username?: string;
+};
+
+/**
+ * Fields expected for authentication based on a username and password.
+ * Both username and password are optional.
+ */
+export type UsernamePassword = {
   /** The password needed to authenticate to the package registry, if any. */
   password?: string;
+} & Username;
+
+/**
+ * Fields expected for token-based authentication.
+ * Both username and token are optional.
+ */
+export type Token = {
   /** The token needed to authenticate to the package registry, if any. */
   token?: string;
-} & Registry;
+} & Username;
+
+/** All authentication-related fields. */
+export type AuthConfig = UsernamePassword & Token;
+
+/**
+ * A package registry configuration includes identifying information as well as
+ * authentication credentials.
+ */
+export type Credential = AuthConfig & Registry;
 
 /** A package registry is identified by its type and address. */
 export type Registry = {